As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) ON DEPARTURE ACFT WAS CLIMBING THRU 11750 FT WHEN CREW HEARD A LOUD BANG AND RUMBLING, UNABLE TO PRESSURIZE. CREW DESCENDED BACK DOWN BELOW 10000 FT AND DIVERTED BACK TO STATION. LANDED 1000 KGS OVERWEIGHT. CHANGED L1 DOOR DEFLECTOR FOR VIBRATION IAW AMM 52-11-28. L1 DOOR ROLLER HEIGHT ADJ C/OUT IAW AMM 52-11-00. CABIN PRESSURIZED TO 5.2 WITH NO FAULTS.